As an example of a heat flux measurement apparatus, Patent Document 1 discloses a heat flux meter provided on a cylinder wall of an engine. In the heat flux meter, a pair of temperature measuring points of a thermocouple are provided on a heat conductive body that is threadably engaged in a threaded hole on the cylinder wall of the engine. The pair of temperature measuring points of the thermocouple are arranged at different locations in a thickness direction of the cylinder wall. The heat flux meter measures a heat flux flowing in the thickness direction of the cylinder wall based on a difference between temperatures measured at the two temperature measuring points.